Edge of Universe?

Does the universe have an edge? Any ideas what’s beyond that edge?
- Muhammed (age 17)
Sir George Monoux College, London

Muhammed-

None of the likely pictures for our universe has an edge. There's good evidence that the universe is almost 'flat'. That means that it's very hard to tell whether it lacks an edge because it’s infinite in all directions or because on some very large scale (at least hundreds of times the length of the visible universe) it wraps around on itself.

You may find that idea of wrapping around strange, but it’s easy to picture for smaller dimensional spaces, like the surface of a sphere.

Of course some more complicated picture of the universe may come up, but for now try to imagine it without an edge.

Mike W.

(published on 10/22/2007)

So what would be on the inside/outside of the flat spherically curved universe?
- Jay (age 30)
Boston, MA

This is the hard part to visualize. In our standard pictures, there is no region outside the universe. The curvature is a way of describing the geometry within the universe itself. Imagining it as part of a higher dimensional space with something outside the hypersphere and something trapped within the hypersphere doesn't add any more information about how things behave in the actual universe.

This is not to say that it's impossible that there could be additional extended spatial dimensions. There are some theories that invoke them. However, they aren't required by the existence of curvature in our own space-time.

Mike W.

(published on 09/30/2010)